Epidemiologic studies from around the world provide evidence for an association between the incidence of lung and other cancers and exposure to airborne aflatoxins in contaminated grain and/or grain dust. Exposure data to assess the potential risk of cancer in farmers and grain workers due to the inhalation of aflatoxin contaminated grain dust are limited by the high cost and poor detection limits of current analytical methods. Exposure data toother toxins (e.g. fumonisins, ochratoxins, vomitoxin, and zearalenones) which can also be commonly found in grain and grain dust. Past analysis of grain dust samples from the midwest and southeast corn growing belt has demonstrated the presence of aflatoxins in high volume air samples of airborne dust. Our preliminary studies indicated that if aflatoxin B1 is present in airborne dust samples during harvest, it continues to be present and may in fact increase throughout subsequent grain handling and animal feeding operations; over 90% of our test farms had detectable airborne aflatoxin by the time the grain bins are cleaned out. Airborne levels in these bins were found in excess of those associated with a historic cohort exposed to airborne aflatoxin currently experiencing excess cancer. The proposed work is an extension of a grant limited largely to laboratory method development which demonstrated the high sensitivity, efficiency, and reliability of the supercritical fluid extraction technique for aflatoxin B1 and fumonisin B1. We propose to develop and test a processing method to extract friable dust from bulk corn which would correlate with the risk of exposure to airborne aflatoxin (and other mycotoxins). This project would test the correlation of two processing methods, one wet and one dry. These would be used in conjunction with a cross-sectional study of 32 farms each conducting 3 activities (harvest, livestock feeding, and grain bin clean- out). These results would also characterize the mean and variability of aflatoxin in farming environments within and among farms, and across and between growing seasons. This data base is intended to guide the development of future epidemiologic study designs. The possibility of climatic patterns of repeated hot and humid growing seasons creates an increasing need to define the possible role of airborne aflatoxins in the etiology of lung or other cancers.